Can't what you are asking for already be accomplished by stroking the selection?
Nope. That is very limited and will stroke everything that you selected. If I want to stroke only, say, 1/3 of an elliptical selection, I can't do that.
The best I can do is construct a path and have it stroked by the program. However, it does not give you any control over the stroke. The best you can do is check the checkbox to enable pressure which will give you a tapered beginning and end section of the stroke. However, when I stroke the path with a wacom pen, I have exact control over the pressure and everything else.
Yeah, I was going to suggest an open path as you said, but that taper on both ends isn't always what you're looking for I know.